|Publication number||US6995446 B2|
|Application number||US 10/318,704|
|Publication date||Feb 7, 2006|
|Filing date||Dec 13, 2002|
|Priority date||Dec 13, 2002|
|Also published as||US20040113183|
|Publication number||10318704, 318704, US 6995446 B2, US 6995446B2, US-B2-6995446, US6995446 B2, US6995446B2|
|Inventors||Ilya Karpov, Manzur Gill|
|Original Assignee||Ovonyx, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (8), Non-Patent Citations (5), Referenced by (13), Classifications (17), Legal Events (7)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This invention relates generally to electronic memories and particularly to electronic memories that use phase change material.
Phase change materials may exhibit at least two different states. The states may be called the amorphous and crystalline states. Transitions between these states may be selectively initiated. The states may be distinguished because the amorphous state generally exhibits higher resistivity than the crystalline state. The amorphous state involves a more disordered atomic structure. Generally any phase change material may be utilized. In some embodiments, however, thin-film chalcogenide alloy materials may be particularly suitable.
The phase change may be induced reversibly. Therefore, the memory may change from the amorphous to the crystalline state and may revert back to the amorphous state thereafter, or vice versa, in response to temperature changes. In effect, each memory cell may be thought of as a programmable resistor, which reversibly changes between higher and lower resistance states. The phase change may be induced by resistive heating.
Because of the high potential storage capacity of phase change memories, and for other reasons, it would be desirable to make phase change memories with as many memory storage locations as possible per unit of area. One issue with existing phase change memories is that an isolation diode may be used between the memory cell itself and the word line. The isolation diode is typically a p-n junction diode. The use of a p-n junction may limit the scalability of the overall memory array inter alia because the p-n junction may not be very vertically scaleable.
Thus, there is a need for better ways to isolate phase change memory elements.
The isolation diode 11 may be a Schottky diode or contact including a metal or metal silicide layer 16 over a substrate 18 that may have a so-called background doping level. The doping levels of the substrate is less than or equal to about 1017 atoms per cubic centimeter in one embodiment. The diode 11 and memory cell 12, bitline 14 and word line 24 may all be formed in the same semiconductor substrate that includes the substrate 18 in one embodiment.
The area of the isolation diode 11 may be defined by oxide or junction isolation regions 20. These regions 20 may be formed by oxide filled trenches, oxidized regions, or by junctions, as a few examples. A guard ring 22 may be formed between the substrate 18 and the isolation regions 20. The guard ring 22 may be doped oppositely to the type of the substrate 18 and, in some embodiments, the guard ring 22 may have slightly higher doping concentration levels than the substrate 18. The guard ring 22 reduces the leakage currents of the isolation diode 11.
By using a Schottky diode in place of a p-n junction diode, a memory that may be more scaleable may be created because of the avoidance of a p-n junction which may not be very vertically scaleable. The guard ring 22 may not create a scalability problem since the doping level of the guard ring 22 is relatively small and the design criteria for the Schottky isolation diode 11 guard ring 22 may be much more scaleable than a p-n junction of a p-n junction diode. The Schottky diode may have much lower doping levels and the guard ring 22 may only handle leakage currents under reverse bias conditions. A normal p-n junction would need to deal with both reverse and forward bias conditions, higher currents, and higher doping levels. As a result, the diode 11 may be more vertically scaleable than conventional isolation diodes, resulting in greater density per unit area in the overall phase change memory 10.
In one embodiment of the present invention, the isolation diode 11 may be formed by initially isolating the region 18 using an appropriate form of isolation 20. A source drain implant that may be utilized on other portions of the substrate may be avoided in the substrate 18. An appropriate masking process may be utilized to form the guard ring 22, for example, by ion implantation. Thus, the existing background doping in the semiconductor substrate 18 may be suitable in some cases for the Schottky diode and all that may be done is to form the guard ring of the opposite conductivity type to that of the substrate 18. Thereafter, the contact 16 may be formed by depositing a metal or forming a metal silicide, as two examples.
While the present invention has been described with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US3718916 *||Feb 10, 1971||Feb 27, 1973||Nippon Electric Co||Semiconductor memory element|
|US3858231 *||Apr 16, 1973||Dec 31, 1974||Ibm||Dielectrically isolated schottky barrier structure and method of forming the same|
|US3924320 *||Oct 18, 1974||Dec 9, 1975||Ibm||Method to improve the reverse leakage characteristics in metal semiconductor contacts|
|US4503521 *||Jun 25, 1982||Mar 5, 1985||International Business Machines Corporation||Non-volatile memory and switching device|
|US4599705 *||Sep 10, 1984||Jul 8, 1986||Energy Conversion Devices, Inc.||Programmable cell for use in programmable electronic arrays|
|US5166901 *||Feb 26, 1991||Nov 24, 1992||Raytheon Company||Programmable memory cell structure including a refractory metal barrier layer|
|US6066884 *||Mar 19, 1999||May 23, 2000||Lucent Technologies Inc.||Schottky diode guard ring structures|
|US20030128134 *||Mar 8, 1999||Jul 10, 2003||Robert A. Fierro||Utility meter interface system|
|1||Ha, Y.H., Yi, J.H., Horii, H., Park, J.H., Joo, S.H., Park, S.O., Chung, U-In and Moon, J.T., "An Edge Contact Type Cell for Phase Change RAM Featuring Very Low Power Consumption," presented at IEEE 2003 Symposium on VLSI Technology, Kyoto, Japan, Jun. 12-14, 2003.|
|2||Horii, H., Yi, J.H., Park, J.H., Ha, Y.H., Baek, I.G., Park, S.O., Hwang, Y.N., Lee, S.H., Kim, Y.T., Lee, K.H., Chung, U-In and Moon, J.T., "A Novel Cell Technology Using N-doped GeSbTe Films for Phase Change RAM," presented at IEEE 2003 Symposium on VLSI Technology, Kyoto, Japan, Jun. 12-14, 2003.|
|3||Hwang, Y.N., Hong, J.S., Lee, S.H., Ahn, S.J., Jeong, G.T., Koh, G.H., Kim, H.J., Jeong, W.C., Lee, S.Y., Park, J.H., Ryoo, K.C.., Horii, H., Ha, Y.H., Yi, J.H., Cho, W.Y., Kim, Y.T., Lee, K.H., Joo, S.H., Park, S.O., Jeong, U.I., Jeong, H.S. and Kim, Kinam, "Completely CMOS-Compatible Phase-Change Nonvolatile RAM Using NMOS Cell Transistors," presented at 2003 19<SUP>th </SUP>IEEE Non-Volatile Semiconductor Memory Workshop, Monterey, California, Feb. 26-20, 2003.|
|4||Hwang, Y.N., Hong, J.S., Lee, S.H., Ahn, S.J., Jeong, G.T., Koh, G.H., Oh, J.H., Kim, H.J., Jeong, W.C., Lee, S.Y., Park, J.H., Ryoo, K.C., Horii, H., Ha, Y.H., Yi, J.H., Cho, W.Y., Kim, Y.T., Lee, K.H., Joo, S.H., Park, S.O., Chung, U.I., Jeong, H.S. and Kim, Kinam, "Full Integration and Reliability Evaluation of Phase-change RAM Based on 0.24 mm-CMOS Technologies," presented at IEEE 2003 Symposium on VLSI Technology, Kyoto, Japan, Jun. 12-14, 2003.|
|5||Karpov et al., U.S. Appl. No. 10/319,183, filed Dec. 13, 2002, entitled "Isolating Phase Change Memory Devices".|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US7745812||Jun 21, 2007||Jun 29, 2010||Qimonda North America Corp.||Integrated circuit including vertical diode|
|US7829879||Feb 19, 2008||Nov 9, 2010||Qimonda Ag||Integrated circuit including U-shaped access device|
|US7834340||Jul 3, 2008||Nov 16, 2010||Samsung Electronics Co., Ltd.||Phase change memory devices and methods of fabricating the same|
|US7838860||Jun 21, 2007||Nov 23, 2010||Qimonda Ag||Integrated circuit including vertical diode|
|US7994536||Feb 19, 2008||Aug 9, 2011||Qimonda Ag||Integrated circuit including U-shaped access device|
|US8284596||Jun 9, 2008||Oct 9, 2012||Qimonda Ag||Integrated circuit including an array of diodes coupled to a layer of resistance changing material|
|US8586960||Jun 19, 2008||Nov 19, 2013||International Business Machines Corporation||Integrated circuit including vertical diode|
|US9064794||Nov 7, 2013||Jun 23, 2015||International Business Machines Corporation||Integrated circuit including vertical diode|
|US20080272354 *||May 4, 2007||Nov 6, 2008||Thomas Nirschl||Phase change diode memory|
|US20080315172 *||Jun 21, 2007||Dec 25, 2008||Thomas Happ||Integrated circuit including vertical diode|
|US20090008622 *||Jul 3, 2008||Jan 8, 2009||Samsung Electronics Co., Ltd.||Phase Change Memory Devices and Methods of Fabricating the Same|
|US20090206315 *||Feb 19, 2008||Aug 20, 2009||Qimonda Ag||Integrated circuit including u-shaped access device|
|US20090206316 *||Feb 19, 2008||Aug 20, 2009||Qimonda Ag||Integrated circuit including u-shaped access device|
|U.S. Classification||257/484, 257/311, 257/E27.004, 257/E29.338, 257/310, 365/105|
|International Classification||H01L29/872, H01L29/76, H01L27/24|
|Cooperative Classification||H01L45/06, H01L27/2409, G11C2213/72, G11C13/0004, H01L29/872|
|European Classification||G11C13/00R1, H01L29/872, H01L27/24|
|Mar 31, 2003||AS||Assignment|
Owner name: OVONYX, INC., IDAHO
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:KARPOV, ILYA;GILL, MANZUR;REEL/FRAME:013906/0310;SIGNINGDATES FROM 20030319 TO 20030320
|Sep 14, 2009||REMI||Maintenance fee reminder mailed|
|Feb 5, 2010||SULP||Surcharge for late payment|
|Feb 5, 2010||FPAY||Fee payment|
Year of fee payment: 4
|Mar 13, 2013||FPAY||Fee payment|
Year of fee payment: 8
|Dec 8, 2015||AS||Assignment|
Owner name: CARLOW INNOVATIONS LLC, VIRGINIA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:OVONYX, INC.;REEL/FRAME:037244/0954
Effective date: 20150731
|Jul 18, 2016||AS||Assignment|
Owner name: OVONYX MEMORY TECHNOLOGY, LLC, VIRGINIA
Free format text: CHANGE OF NAME;ASSIGNOR:CARLOW INNOVATIONS, LLC;REEL/FRAME:039379/0077
Effective date: 20160708